Radio IC device

ABSTRACT

A radio IC device includes a flexible dielectric base, a radiation element that is a metal film or a metal foil wrapped around the dielectric base, and a radio IC element mounted on the radiation element. The radiation element includes, in a portion other than a portion where the radio IC element is disposed, a bonded portion that is bonded to the dielectric element and a non-bonded portion that is not bonded to the dielectric element. The radio IC element is arranged to be directly opposed to the dielectric element with the portion of the radiation element where the radio IC element is disposed not bonded to the dielectric base.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radio IC device, and more particularly to a radio IC device preferably for use in an RFID (radio frequency identification) system.

2. Description of the Related Art

As a system for managing information about articles, in recent years, non-contact communication by use of an electromagnetic field effect is performed between a reader-writer that generates an induction field and RFID tags (which are also referred to as radio IC devices) attached to articles so as to send and receive certain information. Each of the RFID tags stores certain information, and includes a radio IC chip for processing predetermined radio signals and an antenna (radiation element) for sending and receiving high-frequency signals. The RFID tags are used while being stuck to the individual articles to be managed (or the wrappings around the respective articles).

As one of this kind of RFID tags, a metal-compatible tag that operates even while being stuck to the surface of a metal article is disclosed by Japanese Patent Laid-Open Publication Nos. 2006-053833 and 2007-272264. The metal-compatible tag is fabricated by winding a metal pattern, which functions as an antenna, around a dielectric base in the shape of a rectangular parallelepiped. The surfaces of articles, which RFID tags of this type are to be attached to, have various shapes. These RFID tags need to be attachable to, for example, curved surfaces of gas canisters and the like. Such a metal-compatible tag is used while being housed in a flexible case for the purpose of protection.

However, even if the dielectric base is made of a flexible material, a bend of the dielectric base may cause stress concentration on the radio IC chip and may damage the radio IC chip.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide a radio IC device that, even when attached to a curved surface, reliably maintains a shape that is appropriate for a curved surface so that a radio IC element will not be damaged.

A radio IC device according to a preferred embodiment of the present invention includes a flexible dielectric base; a radiation element including a metal film or a metal foil wrapped around the dielectric base; and a radio IC element mounted on the radiation element. The radiation element includes, in a portion other than a portion where the radio IC element is disposed, a bonded portion that is bonded to the dielectric element and a non-bonded portion that is not bonded to the dielectric element. The radio IC element is arranged to be directly opposed to the dielectric element with the portion of the radiation element where the radio IC element is disposed not bonded to the dielectric base.

When the radio IC device is stuck to a curved surface of an article (metal body), the dielectric base may be bent forcedly so as to cause stress. Even in such a case, since the radiation element has a non-bonded portion that is not bonded to the dielectric base besides the portion where the radio IC element is disposed, the radio IC element is prevented from directly receiving the stress caused by stretch and contraction of the radiation element.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a radio IC device according to a first preferred embodiment of the present invention.

FIG. 2 is a plan view of a radiation element and an IC element that are included in the radio IC device.

FIGS. 3A and 3B show a state where the radiation element with the IC element mounted thereon is laminated with a resin film, FIG. 3A being a plan view and FIG. 3B being a front view.

FIG. 4 is a sectional view of a radio IC device according to a second preferred embodiment of the present invention.

FIG. 5 is a sectional view of a radio IC device according to a third preferred embodiment of the present invention.

FIG. 6 is a sectional view of a radio IC device according to a fourth preferred embodiment of the present invention.

FIG. 7 is a sectional view of a radio IC device according to a fifth preferred embodiment of the present invention.

FIG. 8 is a sectional view of a radio IC device according to a sixth preferred embodiment of the present invention.

FIG. 9 is a sectional view of a radio IC device according to a seventh preferred embodiment of the present invention.

FIG. 10 is a sectional view of a radio IC device according to an eighth preferred embodiment of the present invention.

FIG. 11 is a perspective view of a radio IC device according to a ninth preferred embodiment of the present invention.

FIG. 12 is a sectional view of the radio IC device according to the ninth preferred embodiment of the present invention.

FIG. 13 is a perspective view of a radio IC device attached to a gas canister.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Radio IC devices according to some preferred embodiments of the present invention will be hereinafter described with reference to the accompanying drawings. In the drawings, same elements and members are provided with the same reference marks, and repetitious descriptions thereof are omitted.

First Preferred Embodiment

A radio IC device 1A according to a first preferred embodiment is preferably for use in UHF communication. As shown by FIG. 1, the radio IC device 1A preferably includes a dielectric base 21, a radiation element 30 twisted or wrapped around the dielectric base 21 to extend in the lengthwise direction of the dielectric base 21, and a radio IC element 40 mounted on (and electrically or electromagnetically connected to) the radiation element 30.

The dielectric base 21 preferably has an elongated rectangular or substantially rectangular parallelepiped shape and is made of a dielectric material, which may be insulating or magnetic, such as fluororesin, urethane resin or the like. The dielectric base 21 is flexible. The radiation element 30 preferably is made of a flexible metal material such as a copper foil, an aluminum foil or the like. The radiation element 30 has a width slightly smaller than the width of the dielectric base 21, and the radiation element 30 is arranged on the dielectric base 21 so as to extend from an upper surface to a lower surface of the dielectric base 21 through both end surfaces. The radiation element 30 includes a bonded portion, which is bonded to the dielectric base 21, in a portion other than the portion where the radio IC element 40 is disposed. Also, the radiation element 30 includes a non-bonded portion, which is not bonded to the dielectric base 21, besides the non-bonded portion where the radio IC element 40 is disposed. Specifically, in the first preferred embodiment, the radiation element 30 is joined to the dielectric base 21 preferably via an adhesive 22 (which may be alternatively a double-faced adhesive tape or the like) at several spots on the lower surface of the dielectric base 21. For the convenience sake, in FIG. 1, the portion of the radiation element 30 that is not bonded to the dielectric base 21 is shown as a portion spaced from the dielectric base 21. This also applies to FIGS. 4 to 10 and 12.

As shown by FIG. 2, an opening 31 and a slit 32 are preferably located in a central portion of the radiation element 30, and the radio IC element 30 is mounted on (fitted to) feed sections 32 a and 32 b that are defined by opposite sides of the slit 32, respectively. The radio IC element 40 is configured to process RF signals. The radio IC element 40 preferably includes a clock circuit, a logic circuit, a memory circuit, etc., and necessary information is stored in the radio IC element 40. The connections of the radio IC element 40 to the feed sections 32 a and 32 b are realized by electromagnetic coupling or by electrical direct connection (DC) by use of solder bumps or the like. The radio IC element 40 is mounted on a back side of the radiation element 30, so that the radio IC element 40 is directly opposed to the upper surface of the dielectric base 21. In this and the following preferred embodiments, the IC element 40 preferably is of an IC chip type; however, the IC element 40 may include an IC chip and a feed circuit board incorporating a resonance circuit having a predetermined resonance frequency.

As shown by FIGS. 3A and 3B, the radiation element 30 (more specifically, one main surface of the radiation element 30) may be laminated with a flexible resin film 35. In this case, the radiation plate 30 laminated with the resin film 35 is wrapped around the dielectric base 21 with the radiation plate 30 inside. The lamination of the radiation element 30 with the resin film 35 facilitates handling of the radiation element 30 during an assembly process. Alternatively, the radiation element 30 may be formed by metal thin film formation by applying conductive paste on a resin film 35.

In this specification, the radiation element 30 preferably includes both a radiation element made of only a metal foil and a radiation element laminated with a flexible sheet (including paper).

Now, the function of the radio IC device as communication means is briefly described. When a predetermined high-frequency signal is transmitted from the radio IC element 40 to the feed sections 32 a and 32 b, current crowding occurs around the opening 31. The portion where the current crowding occurs functions as a loop-shaped magnetic-field electrode and has a specified potential difference from the feed sections 32 a and 32 b. The specified potential difference between the loop-shaped magnetic-field electrode and the feed sections 32 a and 32 b spreads on the upper surface of the radiation element 30, and there is provided a potential difference between the upper surface and the lower surface of the radiation element 30. As a result, the upper surface of the radiation element 30 functions as a patch antenna.

In this way, the signal is fed from the feed sections 32 a and 32 b, and the characteristic (for example, broadband frequency characteristic) of the signal can be transmitted to an external device through the radiation element 40 with no change. Also, when the radiation element 30 receives a high-frequency signal from an external device, currents are induced around the opening 31, and power is fed to the radio IC element 40 through the feed sections 32 a and 32 b. In this case, the loop-shaped magnetic-field electrode carries out impedance matching between the radio IC element 40 and the radiation element 30.

Electromagnetic-field radiation from the radiation element 30 by itself is weak, and only short-distance communication is possible. When the radio IC device 1A is stuck to a metal body, the lower surface of the radiation element 30 is capacitively coupled with the metal body, and a strong electromagnetic field is radiated from the metal body in a direction perpendicular or substantially perpendicular to the surface of the metal body. Consequently, communication with a distant reader-writer becomes possible. The capacity between the radiation element 30 and the metal body may be infinite. In other words, the lower surface of the radiation element 30 may be electrically connected to the metal body directly.

When the radio IC device 1A is stuck to a plane surface of an article, no problems occur. As shown by FIG. 13, however, there may be a case wherein the radio IC device 1A is stuck to a curved surface of an article like a gas canister 60. When the radio IC device 1A is stuck to a curved surface, the radio IC device 1A bends in the lengthwise direction because the dielectric base 21 and the radiation element 30 are flexible.

When the dielectric base 21 and the radiation element 30 bend as shown in FIG. 13, the upper surface of the dielectric base 21 and the upper surface of the radiation element 30 stretch, and the lower surfaces thereof contract. Since the radio IC element 40 is located between the upper surface of the dielectric base 21 and the radiation element 30, stress concentrates on the radio IC element 40. In the first preferred embodiment, since the radiation element 30 has non-bonded portions that are not bonded to the dielectric base 21 besides the portion wherein the radio IC element 40 is disposed, the radio IC element 40 is prevented from directly receiving stress caused by stretch and contraction of the radiation element 30 accompanying a bend of the dielectric base 21. Thus, even when the radio IC device 1A is stuck to a curved surface, the radio IC device 1A is readily maintained in a shape appropriate for the curved surface, and damage on the radio IC element 40 is prevented.

Second Preferred Embodiment

In a radio IC device 1B according to a second preferred embodiment, as shown by FIG. 4, the radiation element 30 is wrapped around the dielectric base 21 such that the radio IC element 40 mounted on the radiation element 30 is located on the upper surface of the dielectric base 21, and the radiation element 30 is joined to the dielectric base 21 preferably via an adhesive 22 at both the end surfaces of the dielectric base 21. The remaining portion of the radiation element 30 is not bonded to the dielectric base 21. Except for this point, the structure of the radio IC device 1B is preferably the same as the structure of the radio IC device 1A according to the first preferred embodiment. Like in the radio IC device 1A according to the first preferred embodiment, in the radio IC device 1B according to the second preferred embodiment, since the radiation element 30 includes non-bonded portions besides the portion where the radio IC element 40 is disposed, the radio IC element 40 is prevented from directly receiving stress caused by stretching and contraction of the radiation element 30 accompanying a bend of the dielectric base 21.

Third Preferred Embodiment

In a radio IC device 1C according to a third preferred embodiment, as shown by FIG. 5, the radiation element 30 is wrapped around the dielectric base 21 such that the radio IC element 40 mounted on the radiation element 30 is located on the upper surface of the dielectric base 21, and the radiation element 30 is joined to the dielectric base 21 preferably via an adhesive 22 at several spots on the upper surface of the dielectric base 21. The remaining portion of the radiation element 30 is not bonded to the dielectric base 21. Except for this point, the structure of the radio IC device 1C is the same as the structure of the radio IC device 1A according to the first preferred embodiment. Like in the radio IC device 1A according to the first preferred embodiment, in the radio IC device 1C according to the third preferred embodiment, since the radiation element 30 includes non-bonded portions besides the portion where the radio IC element 40 is disposed, the radio IC element 40 is prevented from directly receiving stress caused by stretching and contraction of the radiation element 30 accompanying a bend of the dielectric base 21.

Fourth Preferred Embodiment

In a radio IC device 1D according to a fourth preferred embodiment, as shown by FIG. 6, the radiation element 30 is wrapped around the dielectric base 21 such that the radio IC element 40 mounted on the radiation element 30 is located on the upper surface of the dielectric base 21, and the radiation element 30 is joined to the dielectric base 21 preferably via an adhesive 22 at almost the entire upper surface of the dielectric base 21. The remaining portion of the radiation element 30 is not bonded to the dielectric base 21. Except for this point, the structure of the radio IC device 1D is preferably the same as the structure of the radio IC device 1A according to the first preferred embodiment. Like in the radio IC device 1A according to the first preferred embodiment, in the radio IC device 1D according to the fourth preferred embodiment, since the radiation element 30 includes non-bonded portions besides the portion where the radio IC element 40 is disposed, the radio IC element 40 is prevented from directly receiving stress caused by stretching and contraction of the radiation element 30 accompanying a bend of the dielectric base 21.

Fifth Preferred Embodiment

In a radio IC device 1E according to a fifth preferred embodiment, as shown by FIG. 7, the radiation element 30 is wrapped around the dielectric base 21 such that the radio IC element 40 mounted on the radiation element 30 is located on the upper surface of the dielectric base 21, and the radiation element 30 is joined to the dielectric base 21 preferably via an adhesive 22 at almost the entire lower surface of the dielectric base 21. The remaining portion of the radiation element 30 is not bonded to the dielectric base 21. Except for this point, the structure of the radio IC device 1E is preferably the same as the structure of the radio IC device 1A according to the first preferred embodiment. Like in the radio IC device 1A according to the first preferred embodiment, in the radio IC device 1E according to the fifth preferred embodiment, since the radiation element 30 includes non-bonded portions besides the portion where the radio IC element 40 is disposed, the radio IC element 40 is prevented from directly receiving stress caused by stretch and contraction of the radiation element 30 accompanying a bend of the dielectric base 21.

Sixth Preferred Embodiment

In a radio IC device 1F according to a sixth preferred embodiment, as shown by FIG. 8, the radiation element 30 is wrapped around the dielectric base 21 such that the radio IC element 40 mounted on the radiation element 30 is located on the upper surface of the dielectric base 21, and the radiation element 30 is joined to the dielectric base 21 preferably via an adhesive 22 at almost the entire lower surface and both the end surfaces of the dielectric base 21. The remaining portion of the radiation element 30 is not bonded to the dielectric base 21. Except for this point, the structure of the radio IC device 1F is preferably the same as the structure of the radio IC device 1A according to the first preferred embodiment. Like in the radio IC device 1A according to the first preferred embodiment, in the radio IC device 1F according to the sixth preferred embodiment, since the radiation element 30 includes non-bonded portions besides the portion where the radio IC element 40 is disposed, the radio IC element 40 is prevented from directly receiving stress caused by stretching and contraction of the radiation element 30 accompanying a bend of the dielectric base 21.

Seventh Preferred Embodiment

In a radio IC device 1G according to a seventh preferred embodiment, as shown by FIG. 9, the radiation element 30 is wrapped around the dielectric base 21 such that the radio IC element 40 mounted on the radiation element 30 is located on the upper surface of the dielectric base 21, and the radiation element 30 is joined to the dielectric base 21 preferably via an adhesive 22 at almost the entire upper surface and both the end surfaces of the dielectric base 21. The remaining portion of the radiation element 30 is not bonded to the dielectric base 21. Except for this point, the structure of the radio IC device 1G is preferably the same as the structure of the radio IC device 1A according to the first preferred embodiment. Like in the radio IC device 1A according to the first preferred embodiment, in the radio IC device 1G according to the seventh preferred embodiment, since the radiation element 30 includes non-bonded portions besides the portion where the radio IC element 40 is disposed, the radio IC element 40 is prevented from directly receiving stress caused by stretching and contraction of the radiation element 30 accompanying a bend of the dielectric base 21.

Eighth Preferred Embodiment

In a radio IC device 1H according to an eighth preferred embodiment, as shown by FIG. 10, the radiation element 30 is wrapped around the dielectric base 21 such that the radio IC element 40 mounted on the radiation element 30 is located on the upper surface of the dielectric base 21, and the radiation element 30 is joined to the dielectric base 21 preferably via an adhesive 22 at almost the entire upper surface and almost the entire lower surface of the dielectric base 21. The remaining portion of the radiation element 30 is not bonded to the dielectric base 21. Except for this point, the structure of the radio IC device 1H is preferably the same as the structure of the radio IC device 1A according to the first preferred embodiment. Like in the radio IC device 1A according to the first preferred embodiment, in the radio IC device 1H according to the eighth preferred embodiment, since the radiation element 30 includes non-bonded portion besides the portion with the radio IC element 40 mounted thereon, the radio IC element 40 is prevented from directly receiving stress caused by stretch and contraction of the radiation element 30 accompanying a bend of the dielectric base 21.

Ninth Preferred Embodiment

A radio IC device 1I according to a ninth preferred embodiment, as shown by FIGS. 11 and 12, includes a dielectric base 21, a radiation element 30 that are enclosed in an insulating case 10. The radiation element 30 shown in FIG. 12 is the radiation element 30 according to the first preferred embodiment; however, the radiation element 30 may be any one of the radiation elements 30 according to the second to eighth preferred embodiments.

The case 10 is made of, for example, elastomer resin, and the case 10 includes a plate-shaped base 11 and a box-type cover 15. The dielectric base 21 wrapped with the radiation element 30 with the radio IC element 40 mounted thereon is put into the box-type cover 15, and a flange 16 provided on the periphery of the box-type cover 15 is fused to the outer edge of the base 11, such that these elements are integrated. Thus, the case 10 is made of flexible resin, and the case includes an airtight or substantially airtight space 12 in which the dielectric base 21 is placed.

In the radio IC device 11 according to the ninth preferred embodiment, the radio IC element 40 is located on the upper surface of the dielectric case 21. The dielectric base 21 is fixed to the case 10 preferably via an adhesive 23 (which may be alternatively a double-faced adhesive tape or the like) applied between the base 11 of the case 10 and the lower surface of the dielectric base 21. The dielectric base 21 may be fixed to the case 10 at any portion other than the portion where the radio IC element 40 is located, and the remaining portion of the dielectric base 21 is spaced from the inner surface of the case 10.

In the ninth preferred embodiment, the bottom surface of the case 10 is stuck to an article, and when the case 10 is stuck to a curved surface, the case 10, the dielectric base 21 and the radiation element 30 bend due to the flexibility of their own. Like in the above-described preferred embodiments, in the radio IC device 11 according to the ninth preferred embodiment, the radio IC element 40 is prevented from directly receiving stress caused by bends of the dielectric base 21 and the radiation element 30. The dielectric base 21 is fixed to the case 10 at a portion other than the portion where the radio IC element 40 is located, and the remaining portion of the dielectric base 21 is not bonded to the case 10 and is spaced from the inner surface of the case 10. Therefore, the case 10 bends easily, and the bend of the case 10 prevents the dielectric base 21 from receiving a great deal of stress.

Radio IC devices according to the present invention are not limited to the preferred embodiments above, and various changes and modifications are possible within the scope of the present invention.

The dielectric body is not necessarily in the shape of a rectangular or substantially rectangular parallelepiped, and the dielectric body may be made of thermosetting resin, such as rubber, elastomer, epoxy or the like, or thermoplastic resin, such as polyimide or the like, for example. Alternatively, the dielectric body may be made of ceramic such as LTCC under the condition that a concave portion is provided on the surface of the dielectric body so that the dielectric body can have appropriate flexibility. Further, the dielectric body may be a multilayered body.

The RF-signal propagation through the radiation element, and the transmission and reception of RF signals between the radiation element and the radio IC element are not necessarily carried out in the ways described in connection with the preferred embodiments above. There are various ways of signal propagation and various ways of signal transmission and reception adoptable in the radio IC devices. The shape and the size of the radiation plate can be designed arbitrarily. Further, the radio IC element may be fitted in a recess made in the dielectric base.

In the radio IC devices according to the preferred embodiments above, the radio IC element is prevented from receiving stress caused by stretching and contraction of the radiation element due to a bend of the dielectric base. Therefore, when any of the radio IC devices is stuck to a curved surface, the radio IC device is reliably maintained in a shape appropriate for the curved surface, and damage on the radio IC element is prevented.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims. 

What is claimed is:
 1. A radio IC device comprising: a flexible dielectric base including a first surface, a second surface, and an end surfaces, the first surface and the second surface facing each other and being connected to one another by the end surface; a radiation element including a metal film or a metal foil wrapped around the dielectric base and extending from the first surface to the second surface through the end surface; and a radio IC element mounted on the radiation element; wherein the radiation element includes, in a portion of the radiation element other than a portion of the radiation element on which the radio IC element is mounted, a bonded portion that is bonded to the dielectric base and a non-bonded portion that is not bonded to the dielectric base; the radio IC element is arranged to be adjacent to the first surface of the dielectric base; the portion of the radiation element on which the radio IC element is mounted and a portion of the radiation element facing the end surface are not bonded to the dielectric base; and a portion of the radiation element facing the second surface is bonded to the dielectric base.
 2. The radio IC device according to claim 1, wherein the radiation element is provided on one main surface of an insulating film.
 3. The radio IC device according to claim 1, further comprising an insulating case that houses the dielectric base, the radiation element and the radio IC element.
 4. The radio IC device according to claim 3, wherein the radio IC element is located on the first surface of the dielectric base; and the dielectric base is bonded to the case at a portion of the dielectric base other than the portion of the dielectric base where the radio IC element is disposed.
 5. The radio IC device according to claim 1, wherein the radio IC element is located on the first surface of the dielectric base.
 6. The radio IC device according to claim 1, wherein the radio IC element is located on the first surface of the dielectric base; and a portion of the radiation element facing the first surface is bonded to the dielectric base.
 7. The radio IC device according to claim 1, wherein the dielectric base has an elongated rectangular or substantially rectangular parallelepiped shape.
 8. The radio IC device according to claim 1, wherein the radiation element has a width that is smaller than a width of the dielectric base.
 9. The radio IC device according to claim 1, further comprising an adhesive arranged to bond the bonded portion to the dielectric base.
 10. The radio IC device according to claim 1, wherein the radiation element includes an opening and a slit located in a central portion thereof.
 11. The radio IC device according to claim 10, wherein feed sections are defined by opposite sides of the slit and the radio IC element is mounted to the feed sections.
 12. The radio IC device according to claim 11, wherein the radio IC element is electrically connected to the feed sections via electromagnetic coupling or direct electrical connection.
 13. The radio IC device according to claim 1, further comprising a flexible resin film disposed on a surface of the radiation element.
 14. The radio IC device according to claim 1, wherein an upper surface of the radiation element functions as a patch antenna.
 15. An article comprising: a curved surface; and the radio IC device according to claim 1 attached to the curved surface.
 16. The article according to claim 15, wherein the radio IC device is bent in a lengthwise direction thereof such that upper surfaces of the dielectric base and the radiation element are stretched, and lower surfaces of the dielectric base and the radiation element are contracted. 